<template>
  <div
    :style="{ cursor, userSelect }"
    class="vue-splitter-container clearfix"
    @mouseup="onMouseUp"
    @mousemove="onMouseMove"
  >
    <pane
      class="splitter-pane splitter-paneL"
      :split="split"
      :style="{ [type]: percent + '%' }"
    >
      <slot name="paneL" />
    </pane>

    <resizer
      :class-name="className"
      :style="{ [resizeType]: percent + '%' }"
      :split="split"
      @mousedown.native="onMouseDown"
      @click.native="onClick"
    />

    <pane
      class="splitter-pane splitter-paneR"
      :split="split"
      :style="{ [type]: 100 - percent + '%' }"
    >
      <slot name="paneR" />
    </pane>
    <div v-if="active" class="vue-splitter-container-mask" />
  </div>
</template>

<script>
import Resizer from './resizer.vue'
import Pane from './pane.vue'

export default {
  name: 'SplitPane',
  components: { Resizer, Pane },
  props: {
    minPercent: {
      type: Number,
      default: 10
    },
    defaultPercent: {
      type: Number,
      default: 50
    },
    split: {
      validator(value) {
        return ['vertical', 'horizontal'].indexOf(value) >= 0
      },
      required: true
    },
    className: {
      type: String,
      default: ''
    }
  },
  data() {
    return {
      active: false,
      hasMoved: false,
      height: null,
      percent: this.defaultPercent,
      type: this.split === 'vertical' ? 'width' : 'height',
      resizeType: this.split === 'vertical' ? 'left' : 'top'
    }
  },
  computed: {
    userSelect() {
      return this.active ? 'none' : ''
    },
    cursor() {
      return this.active
        ? this.split === 'vertical'
          ? 'col-resize'
          : 'row-resize'
        : ''
    }
  },
  watch: {
    defaultPercent(newValue, oldValue) {
      this.percent = newValue
    }
  },
  methods: {
    onClick() {
      if (!this.hasMoved) {
        this.percent = 50
        this.$emit('resize', this.percent)
      }
    },
    onMouseDown() {
      this.active = true
      this.hasMoved = false
      this.$emit('mouseDown', this.percent)
    },
    onMouseUp() {
      this.active = false
    },
    onMouseMove(e) {
      if (e.buttons === 0 || e.which === 0) {
        this.active = false
      }

      if (this.active) {
        let offset = 0
        let target = e.currentTarget
        if (this.split === 'vertical') {
          while (target) {
            offset += target.offsetLeft
            target = target.offsetParent
          }
        } else {
          while (target) {
            offset += target.offsetTop
            target = target.offsetParent
          }
        }

        const currentPage = this.split === 'vertical' ? e.pageX : e.pageY
        const targetOffset =
          this.split === 'vertical'
            ? e.currentTarget.offsetWidth
            : e.currentTarget.offsetHeight
        const percent =
          Math.floor(((currentPage - offset) / targetOffset) * 10000) / 100

        if (percent > this.minPercent && percent < 100 - this.minPercent) {
          this.percent = percent
        }

        this.$emit('resize', this.percent)
        this.hasMoved = true
      }
    }
  }
}
</script>

<style scoped>
.clearfix:after {
  visibility: hidden;
  display: block;
  font-size: 0;
  content: ' ';
  clear: both;
  height: 0;
}

.vue-splitter-container {
  height: 100%;
  position: relative;
}

.vue-splitter-container-mask {
  z-index: 9999;
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
}
</style>
